1. Field of the Invention
According to several primary aspects, the invention pertains in general to a so-called multi-clutch device, possibly a double clutch device, for installation in the power train of a motor vehicle between a drive unit and a gearbox, where the clutch device has a first clutch arrangement assigned to a first gearbox input shaft and a second clutch arrangement assigned to a second gearbox input shaft for the transmission of torque between the drive unit and the gearbox, and where the clutch arrangements are designed as disk clutch arrangements, to which an operating fluid, especially a cooling oil, can be supplied for operation under the action of the operating fluid (especially for wet-running operation). In this context, the idea of the invention pertains especially (but not exclusively) to a clutch device of the type in which the disk clutch arrangements can be actuated hydraulically by means of hydraulic slave cylinders integrated into the clutch device.
2. Description of the Related Art
These types of clutch devices have been proposed by the applicant in various patent applications. Reference can be made by way of example to DE 100 04 179 A1, the disclosure of which is included in its entirety by reference in the present application.
According to this primary aspect, the invention also pertains to a power train, which has a drive unit, a gearbox (possibly a power-shift gearbox) with a first gearbox input shaft and a second gearbox input shaft, and a clutch device of the type indicated above, as well as to a motor vehicle comprising this type of power train. In this context, the invention pertains in particular to the idea of assigning an actuator arrangement and a control unit, which controls the actuator arrangement, to the gearbox, which is preferably designed as a power-shift gearbox, so that the gears assigned to the first and the second gearbox input shafts can be engaged and disengaged.
To prevent the disks (especially disks with linings) from wearing down or burning, it is necessary to lubricate/cool them with an operating fluid (especially a cooling oil). Oils normally used for these types of applications have a low viscosity at their working temperature (approximately 90° C.), so that, when the clutch arrangements are open (pressureless hydraulic actuating cylinder in the case of a hydraulically actuatable clutch arrangement of the NORMALLY OPEN type), the drag torques caused by the oil present between the disks are comparatively low (less than, for example, 2 Nm). If, however, the temperature of the oil is very low (for example, considerably below 0° C.), as may be the case, for example, after the motor vehicle has been shut off overnight in the winter, there is a drastic increase in the viscosity of the oil, resulting in very high drag torques (as high as 25 Nm). In addition to these drag torques, break-loose or loosening torques of up to 50 Nm or more can occur when the disks are sticking together; it is necessary to apply these torques only once, however, at the beginning of vehicle operation, to separate the adhering disks from each other. After these disks have been separated, however, the drag torques persist until the viscosity of the oil has decreased as a result of the warming-up of the engine and the introduction of heat (frictional energy) into the clutch arrangements.
As a result these high drag or adhesion torques, it can become impossible in practice to engage a gear, because the synchronizing devices of the gearbox are usually not designed to overcome such high torques. In the typical case, the synchronizing devices are designed for torques on the order of 5 Nm. If no gears can be engaged or shifted, it is not possible to drive the vehicle.
In German Patent Applications Nos. 101 28 856.5 (Filing Date of the Application: Jun. 15, 2001; title: “Clutch System with at Least One Disk Clutch Arrangement, Power Train with the Clutch System, and Warm-Up Process for the System”) and 101 18 756.4 (Filing Date of the Application: Apr. 17, 2001; title: “Clutch System”), various proposals were made which can at least reduce the severity of the problems described above. The approaches to the solutions and the solutions presented in these applications can also be advantageously applied in conjunction with the proposals offered here in the following. The disclosure content of the two applications cited above is included completely by reference in the disclosure of the present application.